The objective of the project is to obtain, using in vivo and in vitro mammalian systems, informaton useful in evaluating whether of not diagnostic and therapeutic levels of ultrasound induce biological perturbations. An important goal of the project is to elucidate the mechanism whereby ultrasound perturbs biological systems. Chinese hamster cells (in vitro) or Chinese hamster cheek pouch epithelial cells (in vivo) are exposed to ultrasound and assessed for proliferation. Previous research has shown that plant root systems are quite sensitive to ultrasound as evidenced by reductions in growth rates and perturbations in cell progression and macromolecular synthesis and chromosomal morphology. In vitro cells exposed to ultrasound display a dose dependent lysis and reduction in colony forming ability. The significance of these studies to health problems is that ultrasound, while finding increasing use in diagnostic and therapeutic applications, is not known to be "safe" as far as the induction of biological effects is concerned.